The invention relates to a communication device comprising a central unit and at least one station, and also to a communication process between said central unit and said station.
Known communication devices comprise a central unit and stations connected via a communication network. Information exchanges between the stations and the central unit generally take place according to a master-slave communication mode or continuously on events.
In the master-slave exchange mode, the central unit requests information from a station which replies to it by transmitting the requested information back to it. This exchange mode has the advantage of being simple. However, the information flow across the network becomes high and there is a risk of saturation due to the double information flow. Indeed, before each item of information which a station has to transmit to the central unit, there is a request from the central unit to said station.
Transmission of information on events does not require a request from the central unit at each information exchange. In this exchange mode, a station transmits information to the central unit of its own accord when an event is detected by said station. This exchange mode is also simple but the information flow is also liable to be high. If the quantity of data liable to be transmitted by the stations is high, the central unit is in fact liable to receive a large quantity of useless information which congests the communication network and consequently reduces its performances.
The exchange on event mode is well suited to communication devices in which the stations have a small quantity of information to transmit. But when the stations are associated in particular to complex apparatuses such as circuit breakers comprising electronic trip devices or measuring devices or devices for computing several electrical quantities, the master-slave or on-event exchange modes do not allow optimum use of the communication network.